The purpose of this European Registration study is to determine whether Arikayce™ is effective in treating chronic lung infections caused by Pseudomonas aeruginosa in Cystic Fibrosis subjects. The effectiveness, safety and tolerability of Arikayce™ will be compared to TOBI, an inhalation antibiotic already available for use. The study will enroll approximately 300 subjects in clinics in Europe and Canada. Subjects will be required to visit the clinic 9 times (including the Screening visit) over a period of approximately 6 months. No overnight stays at the clinic will be required.